1. Field of the Invention
The present invention relates to post-fermentation kettle hop essences and flavorants, and methods of making and using them. More particularly, it relates to glycosides which are capable of imparting kettle hop essence and flavor (e.g., aroma and taste) to malt beverages.
2. Background of the Art
Hops in brewing mainly add bitterness and impart a hop flavor (e.g., taste and smell) in the final product. Hops are composed of soft resins, hard resins, hop oils, waxes, lipids, and carbohydrates. The soft resins consist of .alpha.-acids and .beta.-acids. The soft resins and a hop oil fraction are extractable by organic solvents, or by liquid and supercritical CO.sub.2. In conventional brewing, the .alpha.-acids are converted into iso-.alpha.-acids which are responsible for the bitterness taste. However, as the character of hop flavor is concerned, its description in beer is subjected to a great deal of debate, but all agree that the hop flavor (or the kettle hop flavor) is an essential part in the total organoleptic impact of beer.
When hops, hop extracts, or a hop oil fraction undergo boiling in wort, the hop oils (terpene and sesquiterpene hydrocarbons) are lost mostly through volatilization. As a result, these hydrocarbons are not found in most beers in significant amounts and therefore are not responsible for kettle hop flavor (V. Peacock and M. Deinzer, ACS Symp. Series 170:119-127, 1981). The surviving hop oil components include some oxidized hop oil compounds in very small quantities. We and other investigators have found that these oxidized compounds have very little effect on the kettle hop flavor (J. Irwin, Proc. Conv. Inst. Brew 20:99-104, 1988; Y. Fukuoka and M. Kowaka, Rep. Res. Lab. Kirin Brew. Co. 26:31-36, 1983).
Hops or a hop oil fraction have often been added after fermentation to maintain such volatile hydrocarbon flavors. This practice is called "dry hopping" (J. G. Guzinski, The New Brewer pp. 19-21, July-August 1989; L. Narzi.beta., et al., Monatsschrift fur Brauwissenschaft 38(10):406-409, 1985). But these hop flavors are not considered to be a true and delicate "kettle hop flavor". In the past, attempts have been made to separate hop oil components into various fractions with the purpose of adding these fractions to unhopped beer in order to achieve kettle hop flavor in the products thus produced. These attempts have all met with failure. We believe that the true "kettle hop flavor" refers to the flavor derived from other hop components either intact or modified during fermentation and not to these volatile or oxygenated hydrocarbons.
Heretofore, the brewer produces a different hopped wort stream for each finished beer product having the desired kettle hop flavor characteristics. This entails using dedicated equipment for each such wort stream. Thus, the brewer is faced with many production, quality control, and financial considerations especially when many different products must be produced.
Understanding the chemistry of kettle hop flavor would have a striking impact on the brewing process for quality and for economy. Our previous work utilizing the hop solids (the residue left when hops are extracted by either liquid/supercritical CO.sub.2 or non-polar organic solvents), or water extracts of hop solids, to achieve a kettle hop flavor in beer convinced us to investigate their composition and transformation. Our approach is different from that of the prior art by not focusing on the components in the volatilized hop oils or a hop oil fraction, but concentrating on the water soluble substances in hops or those water soluble substances remaining in the hop solids.
Thus, a need exists for understanding the chemistry of kettle hop flavor components. Such an understanding would allow the brewer to construct a kettle hop flavor essence which could then be added to an unhopped beer stream to obtain a beer with the desired degree of kettle hop flavoring.